studies on the anatomical structure of stems of willow...

O. ARIHAN, A. GÜVENÇ

535

Turk J Bot

35 (2011) 535-551

© TÜBİTAK

doi:10.3906/bot-1003-50

Studies on the anatomical structure of stems of willow (Salix L.)

species (Salicaceae) growing in Ankara province, Turkey

Okan ARIHAN1,

*, Ayşegül GÜVENÇ2

1Yüzüncü Yıl University, Faculty of Arts and Sciences, Department of Biology, Zeve Campus, Van - TURKEY

2Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Botany, 06100 Tandoğan, Ankara - TURKEY

Received: 29.03.2010

Accepted: 10.03.2011

Abstract: Th is study was conducted on the anatomical structure of the stems of 9 Salix L. (willow) species (9 taxa)

growing in Ankara, Turkey. Th ese taxa are S. triandra L. subsp. triandra, S. alba L., S. excelsa J.F.Gmel., S. fragilis L.,

S. babylonica L., S. caprea L., S. cinerea L., S. pseudomedemii E.Wolf, and S. amplexicaulis Bory & Chaub. Illustrations

and photographs were obtained of microscopic views of cross sections from the stems of each taxon. Th e diff ering

anatomical structures of stems of the Salix species are suitable for use as an additional tool in identifi cation. Our aim was

to contribute information on anatomy for the taxonomy of this highly variable genus. Th e anatomical study of these 9

species does not indicate signifi cant separations in morphological observations but instead yields data that can be used

in taxonomy.

Key words: Willow, Salix, Salicaceae, stem anatomy

Ankara ilinde yetişen söğüt (Salix L.) türlerinin (Salicaceae) gövde anatomilerinin

özellikleri

Özet: Bu çalışma, Ankara ili sınırları içinde yetişen 9 Salix L. (söğüt) türünün (9 takson) gövde anatomileri üzerinde

gerçekleştirilmiştir. Bu taksonlar S. triandra L. subsp. triandra, S. alba L., S. excelsa J.F.Gmel., S. fragilis L., S. babylonica

L., S. caprea L., S. cinerea L., S. pseudomedemii E.Wolf ve S. amplexicaulis Bory & Chaub.’dur. Her bir taksonun gövde

kesitlerinin mikroskobik görünümlerinin çizimleri ve fotoğrafl arı verilmiştir. Salix türlerinde farklı anatomik özellikler

bu türlerin teşhisinde ek veri olarak kullanılabilecek niteliktedir. Bu çalışmanın, yüksek derecede varyasyon gösterebilen

bu cinsin taksonomisine anatomik olarak katkıda bulunması hedefl enmiştir. Dokuz takson üzerindeki çalışmanın

anatomik bulguları morfolojik verilerde gözlenen belirgin ayrımlara neden olmamakla birlikte taksonomik açıdan

kullanılabilecek sonuçlar sunmuştur.

Anahtar sözcükler: Söğüt, Salix, Salicaceae, gövde anatomisi

Research Article

* E-mail: [email protected]

Studies on the anatomical structure of stems of willow (Salix L.) species (Salicaceae) growing in Ankara province, Turkey

536

Introduction

Th e species of willow (Salix L.), belonging to the family Salicaceae, comprise deciduous and dioecious trees or shrubs. Th ere are about 450 species of Salix known from all around the world (Argus, 1997); due to the complexity of the genus, however, classifi cation remains diffi cult and there is some disagreement among authors regarding the exact number of species (Fang et al., 1999; Skvortsov, 1999; Ohashi, 2001; Heywood et al., 2006; Mabberly, 2008). Members of this group are found naturally or are planted at wetlands, marshes, river banks, and the sides of streams. Under suitable conditions, they are able to grow quickly. Turkey is rich in a number of willows species; including those that were introduced, 28 species grow in the country and 2 of them are endemic to Turkey (Skvortsov & Edmondson, 1970; Donner, 1990; Güner & Zielinski, 1993; Güner, 2000). Willows are an important group of plants because of their ecological, economical, and medicinal properties. In many countries of the world, including Turkey (Baytop, 1999), willow bark (Cortex Salicis) was commonly used as an antiinfl ammatory, analgesic, and antipyretic agent before the discovery of aspirin (acetylsalicylic acid), and it is still used in herbal remedies (Wichtl & Bisset, 1994; Commission, 1998). Willow is a species that also has many traditional uses because of its role in ethnobotanical practices, such as basketry production.

In addition to its phenotypical plasticity, the easy hybridisation of willows creates problems for the accurate identifi cation and classifi cation of specimens. Th e taxa of Salix are dioecious and many species have diff erent times of development for fl owers and leaves, making it diffi cult to observe all of the relevant characters on a single plant or specimen. Th e fl ower of Salix is furthermore too simple to aff ord adequate characters for taxonomy. Th erefore, in addition to morphological characters, additional information, such as anatomical data, may provide help. Anatomic studies are very important for the identifi cation of medicinal plants (Güvenç & Duman, 2010; Güvenç et al., 2011). Th e anatomy of willow stems and leaves has been investigated by numerous authors (Esau, 1965; Metcalfe & Chalk, 1965; Yazgan et al., 1986) and more recent studies aimed to combine the anatomy and physiology of the willows (Maroder et al., 2000; Cooper & Cass, 2001; Dong & Zhang, 2001). In this study, we investigated the stem anatomy of willow

taxa growing in the province of Ankara: S. triandra L. subsp. triandra, S. alba L., S. excelsa J.F.Gmel., S. fragilis L., S. babylonica L., S. caprea L., S. cinerea L., S. pseudomedemii E.Wolf, and S. amplexicaulis Bory & Chaub. Examinations were done on the cross sections of young stems, and possible characters that may aid in the taxonomy of the species are discussed. In the cortex parenchyma, sclerenchymatic elements were observed. In addition to druses, solitary calcium oxalate crystals were investigated. Th e results are supplemented by photographs and illustrations.

Materials and methods

Th e willow taxa used for this study were collected from diff erent localities within Ankara Province. Aft er comparing diff erent specimens from diff erent sites, the best representatives of the species were chosen for investigation. Th e names of the species and information about the collection sites are given in Table 1. Voucher specimens were deposited in the herbarium of Ankara University’s Faculty of Pharmacy (AEF).

Anatomical research materials were preserved in 70% ethanol or used fresh. Cross sections of stems were hand-prepared from young (second year) stems from preserved or fresh material and boiled in Sartur reagent. Sartur reagent contains KI-I, aniline, Sudan III, lactic acid, alcohol, and water (Çelebioğlu & Baytop, 1949). Illustrations were made using a Leitz drawing prism attached to a Leitz-Wetzlar (45°) microscope. Th e cross sections were photographed with an automatic camera attached to an Olympus BX-50 microscope.

Results

Salix triandra subsp. triandra L.

Young stems are circular in cross section (Figure 1). Th e pith appears circular. Epidermal cells are isodiametric, single-layered; outer and inner walls are rather thickened. Th ese cells are covered with thick suberin (Figure 2). Collenchyma is not seen beneath epidermal layer. Cortex parenchyma, which is situated under the epidermis, is formed by thick-walled, oval, and starch-containing cells with a little space between them and the walls of the adjacent cells (Figure 3). No druse or other kind of calcium


537

crystal can be seen within the parenchymatic cells. Inside the cortex parenchyma there are some intracellular spaces. Sclerenchyma are seen within the cortex region as clustered packs and do not form large belts. Th e cells of the cortex parenchyma, which lies beneath the sclerenchyma, are smaller, more fl attened, and contain much less starch, so this area is lighter in appearance. Below this layer, the phloem sclerenchyma is visible and is not as large as the sclerenchyma above. Phloem is composed of small, irregularly shaped, thin-walled cells. Th e cells that form the cambium layer are slender, fl attened, and distinctly formed by 3 cells. Xylem is large and all elements of it are easily visible. Xylem is divided by single-celled horizontal layers of pith ray cells. Th ese cells are seen easily within the xylem but are not dark. Rounded, dense parenchymatic cells of the xylem are seen in abundance when we approach the pith. Pith is formed by rounded parenchymatic cells. Both calcium crystals and starch are observed in this region (Figure 4). All layers of the anatomical structure of the stem can be seen in Figures 2 and 5.

Table 1. Locations of the studied Salix species.

Species Locality Herbarium number

S. triandra subsp. triandra A4 Ankara: Sincan, along Ankara stream, 800 m, 22.3.2002, O.Arıhan (AEF 22548)

S. alba B4 Ankara: Beynam, Beynam Atatürk Forest, Fındıcak Fountain, 1446 m, 29.4.2001, O.Arıhan (AEF 22668)

S. excelsa B4 Ankara: Lake Eymir, 900 m, 28.8.2001, O.Arıhan (AEF 22707)

S. fragilis B4 Ankara: Beynam, entrance point from the Ankara-Bala road to Beynam Atatürk Forest, 1250 m, 29.4.2001, O.Arıhan (AEF 22536)

S. babylonica B4 Ankara: Lake Eymir, 900 m, 12.4.2001, O.Arıhan (AEF 22716)

S. caprea A4 Ankara: Kızılcahamam, Soğuksu National Park, 1150 m, 31.3.2002, O.Arıhan (AEF 22556)

S. cinerea A4 Ankara: Çubuk-Karagöl, around the lake, 1500 m, 21.4.2002, A.Güvenç & O.Arıhan (AEF 22482)

S. pseudomedemii B4 Ankara: Beynam, Beynam Atatürk Forest, Fındıcak Fountain, 1446 m, 4.4.2001, O.Arıhan (AEF 22725)

S. amplexicaulis A4 Ankara: Kızılcahamam, Soğuksu National Park, 1550 m, 6.11.2001, O.Arıhan (AEF 22616)

1 mm

Figure 1. General view of the cross section of the stem of Salix

triandra subsp. triandra.

0.1 mm

Figure 2. Cross section of the stem of Salix triandra subsp.

triandra, including anatomic properties: 1) epidermis,

2) cortex parenchyma, 3) sclerenchyma, 4) phloem

sclerenchyma, 5) phloem, 6) cambium, 7) xylem, 8)

pith rays, 9) xylem parenchyma, 10) pith.


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Salix alba L.

Young stems are circular in cross section (Figure 6). Th e pith appears almost stellate. Suberin layer is thin, penetrating toward the border between the epidermis

cells (Figure 7). Epidermis, which is composed of a single layer of cells, has thickened walls that form convex projections outside. Cortex parenchyma is formed by thick-walled, spherical or oval-shaped, sometimes rounded, and starch-containing cells with a little intercellular space between the walls of the adjacent cells. Druses, sparsely distributed, can be seen within the parenchymatic cells. Sclerenchyma is seen within the cortex region. Th ese bundles form

Figure 3. Epidermis and parenchyma of Salix triandra subsp.

triandra (10×).


alba.

Figure 4. Pith and xylem cells of Salix triandra subsp. triandra

(10×).


triandra subsp. triandra, including: 1) epidermis, 2)

cortex parenchyma, 3) sclerenchyma, 4) phloem, 5)

cambium, 6) xylem, 7) pith rays, 8) pith (4×).

Figure 7. Cross section of the stem of Salix alba, including

anatomic properties: 1) epidermis, 2) cortex

parenchyma, 3) druse at cortex, 4) sclerenchyma, 5)

phloem, 6) cambium, 7) xylem, 8) pith rays, 9) xylem

parenchyma, 10) pith.

1 mm

0.1 mm


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belts. Th e cells of the cortex parenchyma, which lies beneath the sclerenchyma, are much smaller and contain less starch. Phloem sclerenchyma is visible. Phloem is composed of small to medium, irregularly shaped, thin-walled cells. Th e cells that form the cambium layer are slender, fl attened, and formed by 3 cells. Xylem is divided by single-celled horizontal layers of pith ray cells. Th ese rays are easily seen within the xylem (Figure 8). Xylem is not very large and all elements of it are easily visible (Figure 9). Rounded, sometimes oval, and dense parenchymatic cells of xylem are seen in abundance when we approach the pith. Pith is formed by rounded parenchymatic cells. No calcium crystal or starch is observed in this region. All layers of the anatomical structure of the stem can be seen in Figures 7 and 10.

Salix excelsa J.F.Gmel.

Young stems are circular in cross section (Figure 11). Pith appears stellate. Suberin layer is rather thickened, penetrating toward the border between

the epidermis cells. Epidermis, which is composed of a single layer of cells, has thickened walls that form convex projections outside. Collenchyma is one-layered. Cortex parenchyma, situated beneath the collenchyma, is formed by thick-walled, spherical or oval-shaped, sometimes rounded, starch-containing cells with a little intercellular space between the walls of adjacent cells. Druses are dense and can be seen within the parenchymatic cells (Figure 12). Sclerenchyma is seen within the cortex region (Figure 13). Th ese bundles are scattered and do not form belts. In the vicinity of these bundles are numerous druses. Cells of the cortex parenchyma, which lies beneath the sclerenchyma, are much smaller and contain less starch. Below this layer, phloem sclerenchyma is visible and is also scattered, like the sclerenchyma above. Solitary calcium oxalate crystals exist in some of the cells. Phloem is composed of small, irregularly shaped, thin-walled cells. Cells that form the cambium layer are slender, fl attened, and distinctly

Figure 8. Pith rays and cortex parenchyma cells of Salix alba

(10×).

Figure 10. General cross section of the stem of Salix alba,

including: 1) epidermis, 2) cortex parenchyma, 3)

phloem sclerenchyma, 4) phloem, 5) cambium, 6)

xylem, 7) pith rays, 8) xylem parenchyma, 9) pith

(4×).


excelsa.

Figure 9. Phloem, cambium, and xylem cells of Salix alba (10×).

1 mm


540

formed by 3 cells. Xylem is not very large and all elements of it are easily visible. Xylem is divided by single-celled horizontal layers of pith ray cells. Th ese rays are easily seen within the xylem. Rounded and dense parenchymatic cells of the xylem are seen in abundance when we approach the pith (Figure 14). Pith is formed by rounded parenchymatic cells. Druses can be seen in the pith region. All layers of the anatomical structure of the stem can be seen in Figures 12 and 15.

Salix fragilis L.

Cross sections from young stems are rounded (Figure 16). Pith is almost stellate. Epidermis cells partially covered in suberin. Epidermis is composed

0.1 mm

Figure 12. Cross section of the stem of Salix excelsa, including


parenchyma, 3) druse at cortex, 4) sclerenchyma, 5)



Figure 13. Cortex parenchyma and sclerenchyma of Salix excelsa

(10×).

Figure 14. Pith, xylem cells, and druse of Salix excelsa (10×).

Figure 15. Cross section of the stem of Salix excelsa, including:

1) epidermis, 2) cortex parenchyma, 3) druse, 4)

sclerenchyma, 5) phloem sclerenchyma, 6) phloem,

7) cambium, 8) xylem, 9) pith rays (4×).


541

of a single layer of cells. Collenchyma is single-layered. Cortex parenchyma, situated beneath this layer, has thick-walled, generally oval-shaped (Figure 17), starch-containing cells with intercellular space (Figure 18). Sclerenchyma is situated in cortex region. Th ese bundles are dispersed and cover the stem cortex. Druses are found around those bundles. Small and less starch-containing phloem and phloem sclerenchyma are situated beneath the sclerenchyma. Th is sclerenchymatic layer is dispersed, like the one above. Simple crystals and druses are observed in some of the cells. Cells forming the multicellular cambium layer are thin and fl attened. Xylem is not large and all elements are easily seen. Xylem is formed by a single layer of cells and divided by starch-containing pith rays. Th ese rays are easily observed within xylem. Pith rays do not contain starch in cambium but their starch content becomes visible again when they are located within phloem. Pith is formed by rounded parenchymatic cells (Figure 19). Druses are visible in pith. All layers of the anatomical structure of the stem can be seen in Figures 17 and 20.

Salix babylonica L.

Young stems are circular in cross section (Figure 21). Pith appears as almost stellate. Epidermal cells are isodiametric to rectangular, single-layered; outer and inner walls are rather thickened. Th ese cells are covered with thick suberin. Collenchyma is one-layered. Cortex parenchyma, which is situated beneath the collenchyma, is formed by thick-walled, spherical or oval-shaped, sometimes rounded, starch-containing cells with a little intercellular


fragilis.

Figure 18. Cortex parenchyma cells of Salix fragilis (10×).

1 mm

0.1 mm

Figure 17. Cross section of the stem of Salix fragilis,

including anatomic properties: 1) epidermis, 2)

cortex parenchyma, 3) sclerenchyma, 4) phloem




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space between the walls of the adjacent cells (Figure 22). Druses, which are sparsely distributed, can be seen within the parenchymatic cells. Sclerenchyma is seen within the cortex region. Th ese bundles are scattered and do not form belts. Cells of the cortex parenchyma, which lies beneath the sclerenchyma, are much smaller and contain less starch. Below this

layer, phloem sclerenchyma is visible and is both small in appearance and sparsely distributed. Phloem is composed of small, irregularly shaped, thin-walled cells. Cells that form the cambium layer are slender, multilayered, and fl attened. Xylem is large and all elements of it are easily visible (Figure 23). Xylem

Figure 19. Pith and xylem cells of Salix fragilis (10×).

Figure 20. Cross section of the stem of Salix fragilis, including:

1) epidermis, 2) cortex parenchyma, 3) sclerenchyma,

4) phloem sclerenchyma, 5) phloem, 6) cambium, 7)

xylem, 8) pith rays (4×).

Figure 22. Cross section of the stem of Salix babylonica,

including anatomic properties: 1) epidermis, 2)

cortex parenchyma, 3) sclerenchyma, 4) phloem,

5) cambium, 6) xylem, 7) pith rays, 8) xylem


Figure 21. General view of the stem of Salix babylonica.

Figure 23. Xylem and cambium of Salix babylonica (10×).

1 mm

0.1 mm


543

is divided by single-celled horizontal layers of pith ray cells. Th ese rays are easily seen within the xylem. Rounded and dense parenchymatic cells of xylem are seen in abundance when we approach the pith. Pith is formed by rounded parenchymatic cells. Druses can be seen in the pith region (Figure 24). All layers of the anatomical structure of the stem can be seen in Figures 22 and 25.

Salix caprea L.

Cross sections of young stems are rounded (Figure 26). Pith is rounded. Epidermis is formed of single-layered cells and the walls of those cells make convex projections to the outside. Collenchyma is single-layered. Cortex parenchyma beneath this layer has thick-walled, rounded, starch-containing cells with a little intercellular space. Druses are visible in parenchyma cells (Figure 27). Sclerenchyma exists in

the cortex region. Th ose bundles form a partial belt. Cortex parenchyma cells beneath the sclerenchyma are small and carry less starch. Phloem sclerenchyma may exist beneath this layer and appear dispersed, like the sclerenchyma above. Phloem is formed by small, irregularly shaped, thin-walled cells. Druses are observed in some cells (Figure 28). Cells forming the cambium layer are thin, fl attened, and signifi cantly multilayered (more than 4 layers of cells). All elements of xylem are easily observed.

Figure 24. Starch and druses in the pith of Salix babylonica (10×).


caprea.

Figure 25. Cross section of the stem of Salix babylonica,


sclerenchyma, 4) phloem sclerenchyma, 5) phloem

(4×).

Figure 27. Cross section of the stem of Salix caprea, including


parenchyma, 3) druse, 4) phloem sclerenchyma, 5)



1 mm

0.1 mm


544

Xylem is divided by pith rays in a single row of cells. Th ose rays are easily observed within the xylem. Pith is rounded, formed by parenchymatic cells, and carries druse; starch is not observed (Figure 29). All layers of the anatomical structure of the stem can be seen in Figures 27 and 30.

Salix cinerea L.

Cross sections of young stems are rounded (Figure 31) and have a rough outer structure. Pith is large and not perfectly rounded. Epidermis cells are single-layered. Inner and outer walls of cells are covered by a thick suberin layer. Th is is covered by eglandular trichomes. Collenchyma can be seen and has 1 or 2 layers. Cortex parenchyma, beneath the collenchyma, has thick-walled, rounded, starch-containing cells with intercellular space (Figure 32). Druses are rarely seen in the cortex. Sclerenchyma is seen in the cortex

as large clusters. Phloem sclerenchyma, formed of small bundles, is in a dispersed form. Phloem is formed by small and thin-walled cells. Druses are seen in some cells. Cambium is thin, fl attened, and multilayered with 10 or 11 layers (Figure 33). Xylem is not very large and is frequently divided by pith rays, which are formed by a single row of cells. Th ose rays are easily observed in the xylem. Pith is formed by rounded parenchymatic cells and the intercellular space is very small (Figure 34). Druse and starch are found in pith. All layers of the anatomical structure of the stem can be seen in Figures 32 and 35.

Salix pseudomedemii E.Wolf

Young stems are circular in cross section (Figure 36). Pith appears almost stellate. Epidermis is mostly composed of a single- or sometimes 2-layered cells that are oval. Outer and inner walls of epidermis are covered with a thick suberin layer. Eglandular trichomes are seen in a large percentage (Figure 37). Th ey are simple and unicellular. Trichomes are

Figure 28. Druses in the cortex cells of Salix caprea (10×).

Figure 30. Cross section of the stem of Salix caprea, including:

1) epidermis, 2) cortex parenchyma, 3) druse, 4)

sclerenchyma, 5) phloem sclerenchyma, 6) phloem,

7) cambium, 8) xylem, 9) pith rays, 10) xylem

parenchyma, 11) pith (4×).


cinerea.

Figure 29. Pith and xylem of Salix caprea (10×).

1 mm


545

dense and can reach up to 0.5 mm in length (Figure 38). Collenchyma is generally one-layered. Cortex parenchyma, situated under the collenchyma, is formed by thick-walled, elliptic, starch-containing cells with a little space between the walls of the adjacent cells. Druses can be seen within some of the parenchymatic cells. Inside the cortex parenchyma

Figure 32. Cross section of the stem of Salix cinerea, including

anatomic properties: 1) eglandular trichome, 2)

cortex parenchyma, 3) sclerenchyma, 4) phloem



Figure 33. Xylem, cambium, and phloem of Salix cinerea (10×).

Figure 34. Pith, xylem cells, and druse of Salix cinerea (10×).


pseudomedemii.

Figure 35. Cross section of the stem of Salix cinerea, including:

1) epidermis, 2) cortex parenchyma, 3) sclerenchyma,

4) phloem sclerenchyma, 5) phloem, 6) cambium, 7)


(4×).

0.1 mm

1 mm


546

are some intracellular spaces. Th ese areas are irregular in form and occurrence. Sclerenchyma is seen within the cortex region as big clusters. Th e cells of the cortex parenchyma, which lies beneath the sclerenchyma, are much smaller and contain less starch. Solitary calcium oxalate crystals exist in some cells. Below this layer, phloem sclerenchyma is visible, although it is not as large as the sclerenchyma above. Phloem is composed of small, irregularly

shaped, thin-walled cells. Cambium cells are slender-shaped, fl attened, and multilayered. Xylem is not very large and all of its elements are easily visible. Xylem is divided by single-celled horizontal layers of pith ray cells. Th ese cells are seen as dark rays within the xylem because of their starch content. Rounded, dense, and starch-containing parenchymatic cells of xylem are seen in abundance when we approach the pith. Pith is formed by rounded parenchymatic cells. No calcium crystal or starch is observed in the pith (Figure 39). All layers of the anatomical structure of the stem can be seen in Figures 37 and 40.

Salix amplexicaulis Bory & Chaub.

Cross sections of young stems are rounded (Figure 41). Pith appears rounded and does not constitute a large area. Epidermis is formed of a single layer of generally square-shaped cells. Cells are thick above

0.1 mm

Figure 37. Cross section of the stem of Salix pseudomedemii,

including anatomic properties: 1) eglandular

trichome, 2) epidermis, 3) cortex parenchyma, 4)

druse, 5) sclerenchyma, 6) phloem sclerenchyma,

7) phloem, 8) cambium, 9) xylem, 10) pith rays, 11)

xylem parenchyma, 12) pith.

Figure 38. Eglandular trichomes of Salix pseudomedemii (10×).

Figure 39. Pith and xylem cells of Salix pseudomedemii (10×).


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and below but thin-walled in the sides. No eglandular trichomes are visible. Cortex parenchyma, beneath the epidermis, is formed by thick-walled, generally oval-shaped, rich starch-containing cells with a small intercellular space (Figure 42). Simple crystals are found in some parenchymatic cells (Figure 43). In addition, large or small clusters of sclerenchyma are seen in this region. Cortex parenchyma beneath these bundles has 1 or 2 layers and smaller cells that contain less starch. Beneath this layer, phloem sclerenchyma exists as a thick belt all over the stem. Phloem has small, generally cornered, irregularly shaped, thin-walled cells. Simple crystals are found in phloem parenchyma. Cells forming the cambium are pressed and remarkably 4-5 layered. Xylem constitutes a large area in the stem and all elements of the xylem are easily seen in this area. Xylem is divided by pith rays that are mostly single-layered cells. Pith rays are viewed as dark-coloured rays because of their starch content within the xylem. Pith is centred; xylem cells close to pith are small but larger through the centre. Pith is formed by rounded parenchymatic cells. Starch

Figure 40. Cross section of the stem of Salix pseudomedemii,

including: 1) eglandular trichome, 2) epidermis, 3)

cortex parenchyma, 4) druse, 5) sclerenchyma, 6)

phloem sclerenchyma, 7) phloem, 8) cambium, 9)


(4×).


amplexicaulis.

Figure 43. A crystal in the sclerenchyma of Salix amplexicaulis

(10×).

Figure 42. Cross section of the stem of Salix amplexicaulis,

including anatomic properties: 1) epidermis, 2) cortex

parenchyma, 3) crystal, 4) sclerenchyma, 5) phloem



1 mm

0.1 mm


548

and calcium oxalate crystals are not found in the pith (Figure 44). All layers of the anatomical structure of the stem can be seen in Figures 42 and 45.

Discussion

We have investigated the anatomical structure of young stems of some of the willow species growing in the province of Ankara. Th ese species include S. triandra subsp. triandra, S. alba, S. excelsa, S. fragilis, S. babylonica, S. caprea, S. cinerea, S. pseudomedemii, and S. amplexicaulis. According to the records in the literature, there have not been any studies on the anatomy of willows in Turkey in this context, and such studies are similarly limited in other countries of the world. Th e most detailed information is

given in Metcalfe and Chalk’s (1965) Anatomy of Dicotyledones. Our literature review indicates that only one previous study, “S. alba in Turkey” (Yazgan et al., 1986), provided a cross section of S. alba with schematic and anatomical illustrations. It has been observed that the anatomical structure of the stems of these selected willow species show general similarities. Suberin is found prominently in the outer layer in S. triandra subsp. triandra and S. pseudomedemii. Eglandular trichomes are observed in S. pseudomedemii and S. cinerea, and this anatomical feature is apparently visible in the morphology as well (Arıhan & Güvenç, 2009). Th e epidermis is generally formed by a single layer of cells. In S. pseudomedemii, there can be up to 2 layers of oval cells. Th e cortex parenchyma under the epidermis is formed by rounded, oval, thick-walled cells and is darkly viewed because of starch accumulation. Th ey contain druses (except S. triandra subsp. triandra and S. amplexicaulis). Simple crystals can be seen in some of the cells (S. excelsa, S. fragilis, S. pseudomedemii, and S. amplexicaulis). Th e existence of druses and crystals in nonlignifi ed tissues are in parallel with the information provided by Metcalfe and Chalk (1965). Another common feature shared by all of the species is the existence of intercellular space. From the literature, it is known that there exist some gaps within the periderm and cortex following the secondary growth of wood tissue (Esau, 1965). Such a partition was also observed in our study. Phloem sclerenchyma was found in all of the species except S. alba and S. babylonica. Sclerenchyma, which forms groups within the bark tissue, was observed in all of the species under investigation, and, furthermore, it was seen that in some of the species it is ordered so as to form belts within the stem. Single-celled parenchymatic pith ray cells are visible in all of the species and form a line between the bark and pith. Trachea and tracheids, which form the xylem, are fairly thin-walled. Th ese 2 fi ndings are also parallel to those described by Yazgan et al. (1986). As noted in that study, the cambium is mostly 3- or 4-celled. Druses are found in the pith of S. excelsa, S. fragilis, S. babylonica, S. caprea, and S. pseudomedemii; starch is found in S. pseudomedemii. In the Salix species, pith can be rounded (as in S. triandra subsp. triandra, S. caprea, S. pseudomedemii, and S. amplexicaulis), almost stellate (S. alba, S. babylonica, S. cinerea),

Figure 44. Pith and xylem cells of Salix amplexicaulis (10×).

Figure 45. Cross section of the stem of Salix amplexicaulis,


crystal, 4) sclerenchyma, 5) phloem sclerenchyma, 6)

phloem, 7) cambium, 8) xylem, 9) pith rays (4×).


549

Tab

le 2

. A c

om

par

iso

n o

f cr

oss

sec

tio

ns

fro

m t

he

stem

s o

f 9

wil

low

(Sa

lix)

sp

ecie

s gr

ow

ing

in A

nk

ara,

Tu

rkey

.

Stem

S. t

rian

dra

S. a

lba

S. e

xcel

saS.

fra

gili

sS.

bab

ylon

ica

S. c

apre

aS.

cin

erea

S. p

seu

dom

edem

iiS.

am

plex

icau

lis

Ep

ider

mal

cel

ls

1 l

ayer

ed

rect

angu

lar,

thic

k s

ub

erin

laye

r

1 l

ayer

ed

rect

angu

lar,

3 w

alls

are

thin

, ou

ter

wal

ls t

hic

k

1 l

ayer

ed

1 l

ayer

ed

rect

angu

lar,

thin

1 l

ayer

ed

1 l

ayer

ed,

rect

angu

lar,

thin

wal

led

,

ou

ter

is c

ove

red

wit

h c

uti

cle

1 l

ayer

ed, c

on

vex

1 s

om

etim

es 2

laye

red

, ova

l,

ou

ter

wal

ls

thic

k s

ub

erin

cove

red

1 l

ayer

ed,

rect

angu

lar

shap

ed, b

elo

w

and

up

per

wal

ls

thic

k, s

ides

are

thin

wal

led

Co

rtex

par

ench

yma

cell

rou

nd

ed,

ova

l, st

arch

con

tain

ing

rou

nd

ed, o

val,

thic

k w

alle

d

star

ch, d

ruse

sph

eric

al, o

val,

rou

nd

ed, t

hic

k

wal

led

, sta

rch

,

dru

se, c

ryst

al

ova

l, th

ick

wal

led

, sta

rch

,

dru

se, c

ryst

al

rou

nd

ed, t

hic

k

wal

led

, sta

rch

,

dru

se

rou

nd

ed, t

hic

k

wal

led

, sta

rch

,

dru

se

rou

nd

ed, t

hic

k

wal

led

, sta

rch

,

dru

se

rou

nd

ed, o

val,

th

ick

wal

led

,

star

ch, d

ruse

,

crys

tal

ova

l, th

ick

wal

led

, sta

rch

,

crys

tal

Inte

rcel

lula

r sp

aces

++

++

++

++

few

Ph

loem

scl

eren

chym

a+

+=

+–

++

++

Xyl

em p

aren

chym

ap

ale.

sta

rch

gren

ule

s (*

)st

arch

gra

nu

les+

star

ch g

ran

ule

s(*)

dar

k. s

tarc

h

gran

ule

s+

dar

k. s

tarc

h

gran

ule

s+st

arch

gra

nu

les+

star

ch g

ran

ule

s+d

ark

. sta

rch

gran

ule

s+

dar

k. s

tarc

h

gran

ule

s+

Pit

h c

on

ten

td

ruse

dru

sed

ruse

dru

sed

ruse

, sta

crh

Pit

h s

hap

ero

un

ded

clo

se t

o s

tell

ate

stel

late

stel

late

clo

se t

o s

tell

ate

rou

nd

edcl

ose

to

ro

un

ded

clo

se t

o s

tell

ate

rou

nd

ed

+: p

rese

nt;

–

: ab

sen

ht;

*:

rar

e


550

or stellate (S. excelsa, S. fragilis), as mentioned by

Metcalfe and Chalk (1965). Th is property does not fi t

into a taxonomic order.

According to the characters mentioned in Table

2, S. pseudomedemii shows the greatest diff erence

among these species. Th is fi nding is in parallel

with the taxonomic status of the species (Arıhan

& Güvenç, 2009). A synopsis of the infrageneric

taxa of the Salix species in Turkey has been made

by Skvortsov and Edmondson in Flora of Turkey

(Skvortsov & Edmondson, 1970). Species S. caprea,

S. cinerea, S. pseudomedemii, and S. amplexicaulis are

placed under the subgenus Vetrix Dumort.

Th e other 4 species investigated in this study belong

to the subgenus Salix. None of them contain solitary

calcium oxalate crystals except S. pseudomedemii and

S. excelsa. Th e only species that has no calcium oxalate

crystal is S. triandra subsp. triandra. According to

molecular evidence (Azuma et al., 2000; Trybush

et al., 2008; Chen et al., 2010), S. triandra subsp.

triandra diff ers from other species of subgenus

Salix and forms a distinct clade. Here the molecular

evidence supports our own anatomical fi ndings. Th e

existence of solitary and clustered crystals in the

unlignifi ed tissues is in accordance with Metcalfe

and Chalk (1965). Phloem sclerenchyma is absent in

S. alba and S. babylonica. Densely starch-containing

(dark-coloured) xylem parenchymatic cells are found

in S. alba and S. pseudomedemii. Druse in the pith

can be seen in S. excelsa and S. babylonica. Th e pith

of S. alba is stellate, as described by Metcalfe and

Chalk, whereas the pith of S. triandra subsp. triandra

is round; the other species are variously intermediate.

Among these species, S. alba can be confused with

S. excelsa and S. babylonica because of their general

similarity in terms of morphological appearance. Th e species S. alba and S. babylonica may be especially likely to be confused morphologically. According to our study, most of the characters are shared between these 2 species. Only 2 characters serve to distinguish them: the dark xylem parenchymatic cells in S. alba and the existence of druse in the pith of S. babylonica. Further morphological confusion may occur between S. alba and S. excelsa. Anatomically, S. alba can be distinguished from S. excelsa by the dark xylem parenchyma in S. alba and by the existence of phloem sclerenchyma, druses, and solitary calcium oxalate crystals in S. excelsa.

Th e bark anatomy of the 9 species that we investigated does not indicate a strong division, as is possible to determine from morphological and leaf anatomical characters. Further studies on this subject, however, may yield additional taxonomic data. Th erefore, it is possible to use anatomical characters to diff erentiate between closely related species, although anatomical characters are not always as useful as morphological characters for plant identifi cation. Some of the anatomical features used in this study, such as druses, crystals, or starch content, should be further tested in seasons other than summer, as a shift in the physiological state of the plant can change the accumulation of diff erent materials. In further studies, the stability and reliability of these characters should be investigated since some of these characters may change according to environmental conditions and through hybridisation, a common occurrence in the genus Salix. It is hoped that the present study will provide a basis for future research on willow species in Turkey in addition to contributing to knowledge about those being examined in the greater Mediterranean region.

References

Argus GW (1997). Infrageneric classifi cation of Salix L. (Salicaceae)

in the New World. Systematic Botany Monographs 52.

Arıhan O & Güvenç A (2009). Ankara çevresinde yetişen söğüt (Salix

L.) türleri. Ot Sistematik Botanik Dergisi 16: 15-52.

Azuma T, Kajita T, Yokoyama J & Ohashi H (2000). Phylogenetic

relationships of Salix (Salicaceae) based on rbcL sequence data.

Am J Bot 87: 67-75.

Baytop T (1999). Türkiye’de Bitkiler ile Tedavi (Geçmişte ve Bugün), 2.

Baskı, p. 34. İstanbul: Nobel Tıp Kitapevleri.

Chen JH, Sun H, Wen J & Yang YP (2010). Molecular phylogeny of

Salix L. (Salicaceae) inferred from three chloroplast datasets

and its systematic implications. Taxon 59: 29-37.


551

Commission E Monographs (1998). Complete German Commission E

Monographs: In: Blumenthal M & Buse WR (eds.) Th erapeutic

Guide to Herbal Medicines. American Botanical Council.

Austin, Texas: Lippincott Williams & Wilkins.

Cooper RL & Cass DD (2001). Comparative evaluation of vessel

elements in Salix spp. (Salicaceae) endemic to Athabasca sand

dunes of northern Saskatchewan, Canada. Am J Bot 4: 583-587.

Çelebioğlu S & Baytop T (1949). Bitkisel Tozların Tetkiki İçin Yeni

Bir Reaktif. İstanbul: Farmakognozi Enstitüsü Yayınları, No 10.

Dong X & Zhang X (2001). Some observations of the adaptations of

sandy shrubs to the arid environment in the Mu Us Sandland:

leaf water relations and anatomic features. J Arid Environ 48:

41-48.

Donner J (1990). Distribution maps to P.H. Davis “Flora of Turkey

1-10.” Linzer Biologische Beitrage 2: 381-515.

Esau K (1965). Plant Anatomy, 2nd ed. New York: John Wiley.

Fang Z, Zhao S & Skvortsov AK (1999). Salicaceae. In: Wu Z, Raven

PH (eds.) Flora of China. Beijing – St. Louis: Science Press –

Missouri Botanical Garden Press.

Güner A (2000). Salix L. In: Güner A, Özhatay N, Ekim T & Başer

KHC (eds.) Flora of Turkey and the East Aegean Islands Vol. 11.

Edinburgh: Edinburgh University Press.

Güner A & Zielinski J (1993). Salix rizeensis (Salicaceae): a new

willow from NE Turkey. Karaca Arboretum 1: 1-5.

Güvenç A & Duman H (2010). Morphological and anatomical

studies of annual species of Sideritis L. (Lamiaceae), with notes

on chorology in Turkey. Turk J Bot 34: 83-104.

Güvenç A, Hürkul MM & Erdem A. (2011). Th e leaf anatomy of

Juniperus L. (Cupressaceae) species naturally distributed in

Turkey. Turk J Bot (in press).

Heywood VH, Brummitt RK, Culham A & Seberg O (2006).

Flowering Plant Families of the World. Kew: Royal Botanic

Gardens.

Mabberley DJ (2008). Salix L. In: Mabberley’s Plant Book. A Portable

Dictionary of Plants, Th eir Classifi cation and Uses. Cambridge:

Cambridge University Press.

Maroder HL, Prego IA, Facciuto GR & Maldonado SB (2000). Storage

behaviour of Salix alba and Salix matsudana seeds. Ann Bot

London 86: 1017-1021

Metcalfe CR & Chalk L (1965). Anatomy of the Dicotyledons, Vol. 2.

Oxford: Clarendon Press.

Ohashi H (2001). Salicaceae of Japan. Science Reports of Tohoku

University 4th Series 40: 269-396.

Skvortsov AK (1999). Willows of Russia and Adjacent Countries:

Taxonomical and Geographical Revision (transl. from: Skvortsov

AK (1968) Willows of the USSR: Taxonomic and Geographic

Revision. Nauka, Moscow). Joensuu: Joensuu University.

Skvortsov AK & Edmondson JD (1970). Salix L. In: Davis PH (ed.)

Flora of Turkey and the East Aegean Islands, Vol. 7, pp. 694-716.

Edinburgh: Edinburgh University Press.

Trybush S, Jahodova S, Macalpine W & Karp A (2008). A genetic

study of a Salix germplasm resource reveals new insights into

relationships among subgenera, sections and species. Bioenergy

Research 1: 67-79.

Yazgan M, Uygunlar S, Demiray H & Ay G (1986). Tıbbi Bitkiler

Anatomisi Uygulama Kılavuzu. İzmir: Ege Üniversitesi

Yayınları.

Wichtl M & Bisset NG (1994). Herbal Drugs and Phytopharmaceuticals.

Boca Raton, Florida: CRC Press.

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